Optical transceivers send and receive optical data over an optical link, such as a fiber-optic link. An optical transmitter can include laser driver circuitry to drive a laser diode, such as a light-emitting diode (LED), to create optical pulses or signals on the fiber-optic link from received electronic signals. An optical receiver can include a photodiode to receive the optical signals, which are then converted into electronic signals. Thus, an optical transceiver converts (i) optical signals into analog and/or digital electronic signals and (ii) electronic signals into optical signals.
The receiver (RX) of an optical transceiver generally comprises at least one photodiode or photoelectric detector, at least one TIA and at least one linear amplifier (LA). In addition, the strength of circuit noise is determined by the size of and bias voltage on one or more transistors of the TIA. The bandwidth of the TIA for a predetermined data processing technique can be influenced by the size of the TIA transistor(s) and the bias voltage on the TIA transistor(s). In order to provide TIAs with greater gain and sensitivity, the impedance of feedback resistors can be increased. In general, the gain of TIAs is substantially constant. If the gain of the TIA is too great, the sensitivity requirement for low power optical input signals can be met, but the TIA will be fully overloaded or saturated if optical input power is above a certain power. On the other hand, if the gain of TIA is low, the overload requirement for high power optical input signals can be met, but the TIA will not be sufficiently sensitive if the optical input power is below a certain power.
To improve the capability of the TIA, CN patent application CN1523753A discloses a design using a feedback resistance network to achieve dynamic control of TIA. In the design, the strength of the gain of TIAs can be dynamically regulated by the resistance value of resistors in parallel under the control of a switch. In addition, the overcapacity and sensitivity of TIAs can both be considered.